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Token Expiration

Manage token lifetimes and handle expired tokens gracefully.

30m
0 problems
Topic Progress0%

Token Expiration

Expiration Strategy

Token Lifetime Purpose
Access 15-30 min API access
Refresh 7-30 days Get new access tokens
Session Hours-days Server-side sessions

Expiration Handling

// Client-side
if (response.status === 401) {
    // Token expired, try refresh
    const newToken = await refreshAccessToken();
    if (newToken) {
        return retry originalRequest(newToken);
    } else {
        // Refresh expired, redirect to login
        redirectToLogin();
    }
}

Shorter = More Secure, More Refreshes

Longer = Less Secure, Better UX

Token Management

Token Lifecycle

  1. Generation: Create with short expiry
  2. Validation: Verify signature and claims
  3. Refresh: Exchange refresh token for new access token
  4. Revocation: Invalidate on logout/security events

Storage

  • Access tokens: Memory or short-lived storage
  • Refresh tokens: Secure HTTP-only cookies
  • Revoked tokens: Redis blacklist with TTL

Best Practices

  • Rotate signing keys regularly
  • Implement token binding
  • Monitor token usage patterns

Key Points

  • Understanding Token Expiration is essential for production systems
  • Always consider scalability and maintainability
  • Test thoroughly before deploying to production
  • Monitor performance and set up alerting

Common Patterns

  1. Validation: Always validate input at the boundary
  2. Error Handling: Use structured error responses
  3. Logging: Log key events for debugging
  4. Testing: Unit, integration, and load tests
  5. Documentation: Keep docs updated with code changes

Practice Problems

0/3solved
Implement Token Expiration

Design and implement a solution for Token Expiration in a backend system. Consider scalability, error handling, and production readiness.

Solution
// Token Expiration implementation
// Key aspects: validation, error handling, logging, testing

public class TokenExpiration {
    // Production-ready implementation
}
Token Expiration Edge Cases

Identify and handle edge cases for Token Expiration. What happens under high load, with invalid input, or during failures?

Solution
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotency
Token Expiration Testing Strategy

Write a testing strategy for Token Expiration. Include unit tests, integration tests, and performance tests.

Solution
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injection

Quiz

1. Access token should expire in?

Question 1 options

2. What happens when access token expires?

Question 2 options

3. What is the primary purpose of Token Expiration?

Question 3 options

4. What is a common mistake when implementing Token Expiration?

Question 4 options

Flashcards

Question

Access token lifetime?

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Answer

15-30 minutes

Question

When access token expires?

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Answer

Use refresh token to get new one

Question

What is Token Expiration?

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Answer

Token Expiration is a key concept in backend development.

Question

When to use Token Expiration?

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Answer

Use Token Expiration when building production systems that require reliability, scalability, and maintainability.

Question

Token Expiration best practices

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Answer

Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.

Revision Notes

Key Takeaways

  • 1.Access: 15-30 min, Refresh: 7-30 days
  • 2.Handle 401 with refresh flow
  • 3.Shorter = more secure, more refreshes

Interview Tips

  • •Design token expiration strategy
  • •Handle expired tokens

Cheat Sheet

Token Expiration

  • Access: 15-30 min
  • Refresh: 7-30 days
  • On 401: refresh flow
  • Balance: security vs UX